fix(assets-controller): clean up unused assetsInfo/assetsPrice entries on startup

[Prithpal-Sooriya]

Explanation

AssetsController's assetsInfo and assetsPrice state slices have never had a delete path: metadata and prices are written whenever assets are fetched or detected, but entries are never removed when the assets stop being referenced. Since both slices are persisted, they grow unbounded over time.

This PR adds a cleanup utility that gets invoked once (through #runStartupRefresh)

References

https://consensyssoftware.atlassian.net/browse/ASSETS-3844

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

  

[salimtb]

nit

Suggested change

	for (const slice of [state.assetsInfo, state.assetsPrice]) {
	for (const assetId of Object.keys(slice)) {
	if (isUnused(assetId)) {
	delete slice[assetId];
	}
	}